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/**
***************************************************************************
***************************************************************************
\page page_droption DynamoRIO Option Parser

The \p droption DynamoRIO Extension provides easy-to-use option
declaration and parsing for both clients and standalone programs.

 - \ref sec_droption_setup
 - \ref sec_droption_usage
 - \ref sec_droption_types
 - \ref sec_droption_html
 - \ref sec_droption_aliases
 - \ref sec_droption_reattach

\section sec_droption_setup Setup

To use \p droption with your client simply include this line in your client's
\p CMakeLists.txt file:

\code use_DynamoRIO_extension(clientname droption) \endcode

That will automatically set up the include path.  Then include the header
file:

\code
#include "droption.h"
\endcode

To use \p droption with a non-client, for example with a tool frontend or
other standalone application, simply include the droption.h header file.


\section sec_droption_usage Usage

Simply declare a global instance of \p droption_t of the desired option
value type for each option you wish to support.  Typical value types are \p
bool, integers, or \p std::string.  For example:

\code
using ::dynamorio::droption::DROPTION_SCOPE_CLIENT;
using ::dynamorio::droption::droption_t;

static droption_t<unsigned int> op_x
(DROPTION_SCOPE_CLIENT, "x", 0, 0, 64, "Some param",
 "Longer desc of some param.");

static droption_t<std::string> op_y
(DROPTION_SCOPE_CLIENT, "y", "", "Another param",
 "Longer desc of another param.");

static droption_t<int> op_z
(DROPTION_SCOPE_CLIENT, "foo", 42, "Yet another param",
 "Longer desc of yet another param.");
\endcode

Then, ask for the \p droption_t instances to be filled in from the
passed-in arguments from the user.  In a client using \p dr_client_main(),
or from a standalone application, invoke parse_argv():

\code
using ::dynamorio::droption::droption_parser_t;
std::string parse_err;
if (!droption_parser_t::parse_argv(DROPTION_SCOPE_CLIENT, argc, argv, &parse_err)) {
    dr_fprintf(STDERR, "Usage error: %s", parse_err.c_str());
    dr_abort();
}
\endcode

A standalone application should pass \p DROPTION_SCOPE_FRONTEND rather than
\p DROPTION_SCOPE_CLIENT.

In a client using the legacy \p dr_init(), use the \p dr_parse_options()
function:

\code
std::string parse_err;
if (!dr_parse_options(id, &parse_err)) {
    dr_fprintf(STDERR, "Usage error: %s", parse_err.c_str());
    dr_abort();
}
\endcode

A boolean option \p foo can be negated on the command line using any of the
following prefixes:

- -nofoo
- -no_foo
- --nofoo
- --no_foo

Option values are retrieved with \p get_value:

\code
if (op_x.get_value() > 4) {
}
\endcode

The value set on the command line can be overridden with the \p set_value
function.

\section sec_droption_types Supported Types

\p droption only supports the following standard value types for options:

- int
- long
- long long
- unsigned int
- unsigned long
- unsigned long long
- double
- bool

\p droption also provides some custom value types for options:

- bytesize_t: this class provides an integer type that accepts suffixes
  like 'K', 'M', and 'G' when specifying sizes in units of bytes.

- twostring_t: built-in support for a pair of strings as values.


\section sec_droption_html Automated HTML

To produced automated documentation with the long-format descriptions, we
recommend building a small program that looks something like this:

\code
#include <iostream>
#include "droption.h"
#include "options.h"

using ::dynamorio::droption::droption_parser_t;
using ::dynamorio::droption::DROPTION_SCOPE_ALL;

int
main(int argc, const char *argv[])
{
    std::cout << droption_parser_t::usage_long(DROPTION_SCOPE_ALL,
                                               "- <b>", "</b>\n",
                                               "  <br><i>", "</i>\n",
                                               "  <br>", "\n")
              << std::endl;
    return 0;
}
\endcode

This program can be built and run at documentation generation time to
produce HTML that can then be embedded into Doxygen or other
documentation.

\section sec_droption_aliases Aliases

To support multiple strings to trigger the same option, pass a vector
of strings as the name, with the primary name (the one used in usage
reports) listed first, like this:

\code
droption_t<std::string> op_blocklist(
    // We support the legacy name as an alias for compatibility.
    // We explicitly specity the vector type to avoid ambiguity with iterators
    // when we have just 2 elements in the list.
    DROPTION_SCOPE_CLIENT, std::vector<std::string>({ "blocklist", "blacklist" }),
    IF_WINDOWS_ELSE("ntdll.dll", ""), ":-separated list of libs to ignore.",
    "The blocklist is a :-separated list of library names for which violations "
    "should not be reported.");
\endcode

\section sec_droption_reattach Clearing Accumulated Values on Re-attach

For options that accumulate values
(#dynamorio::droption::DROPTION_FLAG_ACCUMULATE), a
re-attach with a statically linked client will keep the old value from
the prior attach.  The `droption_parser_t::clear_values()` function
can be called from the client on exit or initialization to clear all
the values.

*/
